This application claims a priority of German application 100 34 767.3, filed Jul. 18, 2000, and the contents of that application are incorporated herein by reference.
This invention relates to a lamp, in particular a position lamp for a motor vehicle, having a housing in which at least one light source is arranged and having a light pane covering an opening of the housing.
It is conventional to equip lamps with incandescent bulbs and a reflector to achieve, for example, a desired light-intensity distribution for a position lamp. In the case of motor vehicles, reflectors which produce a uniform emittance of light with a symmetrical light-intensity distribution are used. In the case of aircraft, it is known that when a position lamp is provided on a free end of a wing, for example, different light-intensity distributions in the vertical and horizontal directions are required. One disadvantage of such a known lamp is that the light intensity of the incandescent bulb must be relatively high, because in order to ensure the functionality of the night vision equipment used by pilots, light rays of a certain wavelength must be filtered out by an additional light-absorbing light filter mounted on the lamp. Due to the absorbing effect of the filters, there is self-heating of the incandescent bulb, which shortens the lifetime of the lamp.
It is therefore an object of this invention to improve upon a lamp for motor vehicles such that it is possible to assure that a predetermined light-intensity distribution will be achieved with economical operation and a relatively long lifetime.
According to principles of this invention, in a lamp, in particular a position lamp for a motor vehicle having a housing in which at least one light source is arranged and having a light pane that covers an opening of the housing, a light source is structured as a plurality of light-emitting diodes (LEDs) with an illumination field formed by a plurality of similar first light-emitting diodes provided to create a basic light-intensity distribution, and at least one additional second light-emitting diode provided to produce a preferred light-intensity distribution, so that by superimposing the basic light-intensity distribution on the preferred light-intensity distribution a predetermined total light-intensity distribution is produced.
A particular advantage of this invention is that due to the presence of light-emitting diodes of different luminous properties, it is possible to achieve a basic light-intensity distribution as well as a preferred light-intensity distribution, which can be superimposed to produce a predetermined total light-intensity distribution. A basic idea of this invention is to form an illumination field with a plurality of similarly structured light-emitting diodes with which the basic light-intensity distribution is achieved. A preferred light-intensity distribution can be produced in a certain spatial angle range by additional second light-emitting diodes, usually having a greater power, oriented in a certain preferred direction. By selecting the second light-emitting diodes of the certain light intensity or light-intensity distribution, it is possible to configure a specific total light-intensity distribution in an advantageous manner. A power consumption of the lamp can be reduced and its lifetime greatly increased by using light-emitting diodes. In particular, through the choice of light-emitting diodes, it is possible to achieve a spectrum which stays away from interfering with a wavelength range of night vision equipment. The filter glass is omitted and it is not necessary to use an additional night vision filter.
According to a particular embodiment of this invention, the first light-emitting diodes are combined in a separate basic light module which is a compact unit having a module housing with only two connecting pins. A plurality of first light-emitting diodes is connected together on a light-emitting diode carrier. The first light-emitting diodes may be mounted with a relatively high packing density. By combining the first light-emitting diodes on the light-emitting diode carrier, a separate mechanical and electrical coupling of the basic light module from the housing of the lamp can be created in an advantageous manner. The mounting of the basic light module is simplified because only two electric terminals are provided. By combining the first light-emitting diodes in the module housing, the first light-emitting diodes can be protected mechanically and also can be arranged within the housing of the lamp by the secure mechanical and electronic connection.
According to another embodiment of this invention, the first light-emitting diodes are arranged in a grid on a light-emitting diode carrier plate of the module housing so that a uniformly and broadly-radiated light-intensity distribution can be achieved. The first light-emitting diodes preferably each have a relatively low light intensity. By superimposing a plurality of such regularly arranged first light-emitting diodes, a basic light-intensity distribution having a relatively constant gradient over a spatial angle range can be achieved in an uncomplicated manner.
According to another embodiment of this invention, the basic light module is mounted on a first holding part, and the additional second light-emitting diodes are arranged on a second holding part of the housing, with the holding parts being arranged at an inclination to each other by a predetermined angle. In this way a maximum value of the basic light-intensity distribution on the one hand and the preferred light-intensity distribution on the other hand can be defined in space in an advantageous manner, so that a predetermined total light-intensity distribution is achieved.
According to another embodiment of this invention, the housing of the lamp is arranged on a free end of a wing of an aircraft, where the lamp serves as a position lamp. The second holding part extends perpendicular to the direction of flight, and the second light-emitting diodes mounted on the second holding part are oriented in the direction of flight. The first part extends at an acute angle rearwardly to the second holding part, so that the basic light is emitted substantially in a lateral direction to the longitudinal axis of the vehicle.
According to another embodiment of this invention, a reflector element is arranged at a borderline area between the first and second holding parts, so that beams of light emitted by the second light-emitting diodes are partially reflected by this reflector element. The reflector element thus serves to increase the light intensity emitted by the second light-emitting diodes in certain spatial angles. In addition, the reflector element also has an light-shield function. An edge of the reflector element facing way from the borderline area is oriented with respect to the basic light module so that an exact light-dark border image is achieved at a predetermined angle. By this means a blinding of pilots can be prevented.
According to another embodiment of this invention, the basic light module has a light-transmissive cover in the form of a cupola, or dome, which permits a homogeneous emission characteristic.
According to another embodiment of this invention, an infrared diode is positioned on a base plate oriented in the direction of flight. In this way it is possible to send optical identification patterns between members of a flight group for identification of friend vs. foe. Since the infrared diode projects laterally outward away from the base plate, there is a main direction of emittance perpendicular to the direction of flight, thus preventing a direct blinding of pilots.
According to another embodiment of this invention, the basic light module and the second light-emitting diodes are driven by a common control circuit. The basic light module on the one hand and the second light-emitting diodes on the other hand are connected in parallel, so that a total current, which is delivered as an impressed supply-current amperage from the control circuit to the consumer elements, is determined as a function of the prevailing component currents flowing in branches. The control circuit preferably has a step-down converter and at least one constant current source with which the consumer-dependent supply-current amperage is applied.